7.
Omit the ending period if it comes after a quotation mark that is preceded by a period.

He said: "She said: 'I know what it's like to be dead.'"

8.
Omit them after Roman numerals that are being used as ordinals.

Super Bowl XVI

Etymology -
The word period derives from the Latin periodus, a complete sentence, which in turn derives from the Greek periodos, rounded sentence or period
of time (from peri, around + hodos, journey).Note: Some claim that the punctuation mark was invented by Aristophanes of Byzantium.

Oxford English Dictionary - Its first citation in its punctuation-mark sense is from 1609: "No Commaes but thy Stripes; no Periods But thy Nailes."(J. Davies Holy Roode (1878) 20/2)